Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
h,w=map(int,input().split())
l=[]
v=0

for _ in range(h):
  b=[0 if i=="." else 1 for i in input()]
  v+=b.count(1)
  l.extend([b])

dq=deque([])
dq.append((0,0,1))

while dq:
  x,y,d=dq.popleft()
  if x==w-1 and y==h-1:break
  for (dx,dy) in zip([-1,1,0,0],[0,0,-1,1]):
    nx=x+dx
    ny=y+dy
    if 0<=nx<w and 0<=ny<h and not l[ny][nx]:
      l[ny][nx]=2
      dq.append((nx,ny,d+1))

if x==w-1 and y==h-1:
  print(h*w-v-d)
else:
  print(-1)